This invention relates to a method for making a core for an electrical transformer, and more particularly, a core formed from superimposed packets comprised of relatively thin sheets of an amorphous metal. The invention is also concerned with the core as an article of manufacture.
Amorphous metals having a non-crystalline structure are desired in forming elecromagnetic devices, such as cores for electrical transformers, because of their superior electrical characteristic relative to crystalline steel type metals. The amorphous metals are typically made available on rolls of a continuous relatively thin sheet having a relatively narrow width. The relatively thin sheets have the advantage of correspondingly forming relatively thin laminations of an amorphous metal core to reduce the eddy currents within the amorphous metal core, which, in turn, reduce the electrical losses of the core. However, the relatively thin sheets of amorphous metals have the disadvantages of (1) requiring more laminations to form a desired amorphous metal core, and (2) causing difficulty in handling during the manipulative steps involved in forming an amorphous metal core.
Furthermore, the magnetic properties of the amorphous metals have been found to be deleteriously affected by mechanical stresses such as those created by the fabricating steps of winding and forming the amorphous metals into a desired core shape. See, for example, a technical article entitled, "Strain-Induced Anisotropy in Amorphous Alloys and the Effect of Toroid Diameter on Magnetic Properties"; by F. E. Luborsky et al, published in the IEEE TRANSACTIONS ON MAGNETICS, VOL. MAG-15, No. 6, November 1979.
Accordingly, objects of the present invention are to provide a core formed of amorphous metal and a method of forming the amorphous metal core in which (1) the effective number of laminations of the amorphous metal core are reduced, (2) the difficulties of handling the amorphous metal to perform the manipulative steps of the fabrication process are reduced, and (3) the mechanical stresses induced into the amorphous metal core during its fabrication process are reduced. These and other objects of the present invention are accomplished, in part, by heating and bonding together a plurality of amorphous metal sheets to form packets that are used in fabricating the core.
It is a further object of the present invention to provide for such a bonding operation in which the amorphous metal is maintained within a desired temperature range such that it does not transform from its non-crystalline to a crystalline state.
These and other objects of the invention will become apparent to those skilled in the art upon consideration of the following description of the invention.